a. Field of the Invention
This invention generally relates to the offshore construction art and, more particularly, to the art of erecting a buoyant, very long, large-diameter column and of maintaining the column fully submerged above the sea bottom to allow the column to draw cold water from the sea bottom.
b. The Need for the Invention
An Ocean Thermal Energy Conversion (OTEC) system can provide an inexhaustible electric power source which utilizes the temperature difference between the warm surface water and the cold water found at lower depths in the oceans to produce electricity. Since the oceans cover approximately 70% of the earth's surface, it will be appreciated that they can provide a continuously renewable, non-polluting energy source.
Basically an OTEC system comprises a power plant, a suitable floating platform to house the equipment necessary for running the plant, and energy conversion and utilization subsystems. The power plant can be based on the closed Rankine thermodynamic cycle which utilizes a working fluid such as ammonia, capable of evaporating and condensing over a small temperature range. Warm sea water is pumped into an evaporator where the ammonia liquid is heated and vaporized. The ammonia vapor is fed into a turbo-generator where the thermal energy of the vapor is converted into mechanical energy, and then into electric power. The vapor leaving the turbine is fed into a condenser where it is cooled and condensed into its liquid state. The condenser receives cooling water through and from a very long pipe column which reaches down into the ocean depths where the relatively cold water is found. Condensed ammonia is pressurized and returned to the evaporator thereby completing the Rankine cycle.
It is anticipated that such an OTEC power plant would require approximately 6 million gallons per minute of warm water flow, and an equivalent volume of cold water flow for each 100 MWe of net electric power.
This invention is concerned only with the construction and erection of the cold water pipe column which is required in the above described OTEC power plant. The invention, however, can find utility wherever a very large diameter offshore column is required to be erected from columnar members.
Sites for OTEC electricity generating plants are most suitable in latitudes not more than approximately 20.degree. north and south of the equator. Such sites are available, for example, in the Gulf of Mexico from Florida to Texas. Other suitable sites could be near Hawaii and Puerto Rico.